1. Field of the Invention
The present invention relates to photoresist compositions for a resist flow process and a process for forming a contact hole using the same. In particular, the present invention relates to a photoresist composition comprising a thermal curing agent which cures the photoresist composition at an elevated temperature; and a method for forming a contact hole using the same.
2. Description of the Background Art
Resist flow is a processing technology for forming a fine contact hole which exceeds the resolution of the exposing device.
The resist flow process has recently made remarkable developments and so that it is now used in mass production processes. The technology generally involves an exposure process and a development process. This process forms a photoresist contact hole having a resolution equal to that of the exposing device. The process also includes heating the photoresist to a temperature higher than the glass transition temperature of the photoresist which causes the photoresist to flow. The contact hole gets smaller by the flow of photoresist until a fine contact hole necessary for the integration process is obtained (see FIG. 1).
Thus, the resist flow process makes it possible to obtain contact holes smaller than the resolution of an exposing device. However, one major limitation of the resist flow process is that an excessive thermal flow (i.e., xe2x80x9coverflowxe2x80x9d) covers or destroys the contact hole pattern. The over flow can occur due to several factors including photoresist""s sensitivity to heat, imprecise temperature control, and imprecise control of the flow time. Any one or more of these factors cause an excessive thermal flow, which results in the photoresist covering the contact hole. Such overflow can be seen in FIG. 2, which shows a graph of the baking temperature versus the size of final contact hole. As FIG. 2 shows, the size of a 200 nm contact hole decreases remarkably as the baking temperature increases from 100 xc2x0 C. to 140 xc2x0 C. This decrease in contact hole size is believed to be due to the photoresist undergoing a rapid thermal flow even with a slight increase in temperature.
Attempts to solve the overflow problem by improving the baking process, such as maintaining a uniform baking temperature and/or controlling the precise baking time, have been mostly unsuccessful.
Accordingly, it is an object of the present invention to provide photoresist compositions for a resist flow process.
Another object of the present invention is to provide a resist flow process for forming a photoresist pattern using such photoresist composition.
Still another object of the present invention is to provide a contact hole formation method employing the photoresist pattern formed by the above-described process.